1. Field of the Invention
The present invention relates to a shift position indicating device having means for recommending a proper shift position to a driver of a hybrid vehicle having a manual transmission.
2. Description of the Prior Art
Conventionally known is a shift position indicating device in a vehicle driven by an internal combustion engine, in which an intake negative pressure and a rotational speed of the engine are detected, and an indication of recommending shift-up to a driver of the vehicle is made when the intake vacuum is higher than a threshold pressure and/or when the engine rotational speed is higher than a threshold speed, while an indication of recommending shift-down to the driver is made when the engine rotational speed is extremely lowered (Japanese Patent Publication No. 60-47128 (Kokoku)). This device is designed so that the shift-up is indicated to mainly improve fuel economy when detecting an engine operating condition allowing a change from a present shift position to a shift position higher in gear ratio than the present shift position, and that the shift-down is indicated to avoid engine stall when the engine rotational speed is extremely lowered.
In the above conventional device, the shift-up is not indicated in a high-load running condition such as a hill-climbing condition, and the shift-down is not indicated as far as the engine rotational speed is not extremely lowered, then maintaining a present shift position.
In the case of applying such a shift position indicating device to a hybrid vehicle having an internal combustion engine and a motor as a prime mover, fuel consumption can be improved by indicating the shift-up during normal running. However, during high-load running such as hill climbing, a drive force is assisted by the motor to result in an increase in power consumption, so that electrical energy stored in electrical energy storing means such as a battery is decreased to cause a possibility that the drive assistance by the motor cannot be obtained when required. Further, when the electrical energy stored in the electrical energy storing means is decreased, it is controlled to preferentially store electrical energy into the electrical energy storing means. As a result, a problem that the drive assistance by the motor becomes more difficult to perform, which may deteriorate the running performance during normal running may be deteriorated.
It is accordingly an object of the present invention to provide a shift position indicating device which can accurately recommend a shift position suitable for a hybrid vehicle and can properly maintain the electrical energy stored in the electrical energy storing means.
According to the present invention, there is provided a shift position indicating device for indicating a recommended shift position to a driver of a hybrid vehicle having an engine for driving a drive shaft of said vehicle, a motor for assisting a drive force applied to said drive shaft by electrical energy, said motor having a regenerative function of converting kinetic energy of said drive shaft into electrical energy, and electrical energy storing means for supplying power to said motor and storing electrical energy output from said motor. This sift position indicating device is characterized in the improvement comprising vehicle operating condition detecting means for detecting an operating condition of said vehicle, said vehicle operating condition detecting means having high-load running detecting means for detecting a high-load running condition of said vehicle, and shift-down recommending means for recommending shift-down to said driver according to said operating condition detected by said vehicle operating condition detecting means, said shift-down recommending means recommending the shift-down under the condition that said vehicle is in said high-load running condition.
With this configuration, shift-down is recommended to the driver under the condition that the vehicle is in the high-load running condition, according to the detected vehicle operating condition. Then, the recommended shift-down recommended is carried out by the driver, and the vehicle is accordingly controlled so that the load on the engine to generate a drive force for the vehicle is increased and the load on the motor is decreased. As a result, the continuation of large power consumption by the motor can be prevented to thereby avoid an extreme reduction in electrical energy stored in the electrical energy storing means and to allow proper assistance of the drive force by the motor as required.
Preferably, said high-load running detecting means includes high-load operating condition detecting means for detecting a high-load operating condition of said engine and vehicle speed detecting means for detecting a vehicle speed of said vehicle, and determines that said vehicle is in said high-load running condition when said engine is in said high-load operating condition and a change in said vehicle speed is small.
The condition that xe2x80x9ca change in said vehicle speed is smallxe2x80x9d is detected, for example, by detecting that the deviation between the detected vehicle speed and an average vehicle speed (the deviation=the vehicle speedxe2x88x92the average vehicle speed) is less than or equal to a predetermined deviation. Accordingly, the high-load running condition such as a hill-climbing condition can be accurately detected.
Preferably, said high-load operating condition detecting means determines that said engine is in said high-load operating condition when an intake pipe pressure of said engine is higher than a determination threshold which is set higher with an increase in remaining charge of said electrical energy storing means or when a parameter indicative of driver""s intention of acceleration of said vehicle is greater than a determination threshold which is set higher with an increase in remaining charge of said electrical energy storing means.
Accordingly, the recommendation of more suitable shift position can be effected according to the remaining charge of the electrical energy storing means.
Other objects and features of the invention will be more fully understood from the following detailed description and appended claims when taken with the accompanying drawings.